GPT-5.5 Pro vs GPT-6 Astra
GPT-5.5 Pro Verdict
- GPT-6 Astra (high) leads on quality: 71.9 vs 67.1.
- GPT-6 Astra (high) is stronger in maths, reasoning, agents & tools, coding, composite, knowledge, long context, multimodal.
- GPT-6 Astra (high) is 3.4× cheaper ($20.00 vs $67.50 per 1M blended).
- GPT-6 Astra (high) streams 11.8× faster (47 vs 4 tokens per second).
| Metric | GPT-5.5 Pro (xhigh) | GPT-6 Astra (high) |
|---|---|---|
| BenchLeader Index | 67.1 | 71.9 |
| Maths score | 74.5 | 79.5 |
| Reasoning score | 80.1 | 81.9 |
| Agents & tools score | – | 64.9 |
| Coding score | – | 72.8 |
| Composite score | – | 93.8 |
| Knowledge score | – | 85.1 |
| Long context score | – | 66.5 |
| Multimodal score | – | 71.2 |
| Blended price $/M | $67.50 | $20.00 |
| Output speed | 4 tok/s | 47 tok/s |
| Time to first answer | 3.5 s | 49.2 s |
| Context window | 1.1M | 1.1M |
| FrontierMath Tiers 1–3 | 87.7% | – |
| FrontierMath Tier 4 | 78.0% | 97.6% |
| Terminal-Bench | – | 57.9% |
| SciCode | – | 55.4% |
| WeirdML | – | 92.9% |
| AA Intelligence Index | – | 51.0 |
| AA-LCR | – | 80.0% |
| MMMU-Pro | – | 86.4% |
| AA-Omniscience | – | 43.7 |
| GPQA Diamond (AA) | – | 95.0% |
| Humanity's Last Exam (AA) | – | 53.1% |
| SciCode (AA) | – | 55.4% |
| ARC-AGI-1 | 95.0% | 98.5% |
| ARC-AGI-2 | 84.2% | 92.1% |
| ARC-AGI-3 | – | 99.9% |
| CritPt | 30.6% | 28.9% |
| GDPval (AA) | – | 51.5% |
| τ²-Bench Banking (AA) | – | 40.0% |
| MirrorCode | – | 46.7% |
| DeepSWE | – | 73.2% |
| LMCA | 53.9% | – |
| DTBench | 96.0% | – |
Data as of 2026-09-19. Best configuration of each model; every score links to its source on the model pages.
GPT-5.5 Pro vs GPT-6 Astra: questions
- Is GPT-5.5 Pro better than GPT-6 Astra?
- GPT-6 Astra (high) leads on quality: 71.9 vs 67.1. The BenchLeader Index combines every independent quality benchmark; GPT-6 Astra (high) is ahead overall as of 2026-09-19, but check the category scores for your use.
- Which is cheaper, GPT-5.5 Pro or GPT-6 Astra?
- GPT-6 Astra is cheaper: $20.00 against $67.50 per million tokens, blended at three input tokens per output token.
- Which is faster, GPT-5.5 Pro or GPT-6 Astra?
- GPT-6 Astra streams faster: 47 against 4 output tokens per second.
- Which has the larger context window?
- Both accept 1.1M tokens of context.